Devices, such as light-emitting diodes, are known as devices in which a nanocarbon material is used. In these devices a pair of lead wires are connected to both end portions of a graphene nanoribbon or both end portions of each of a plurality of stacks including groups of graphene nanoribbons which differ in band gap. It is known that the band gap of a graphene nanoribbon changes according to its width, its thickness, its edge state, doping, or the like.
Furthermore, a Schottky barrier diode in which a pair of metals, such as titanium (Ti) and platinum (Pt), are connected to both end portions of a single-layer carbon nanotube is known.
International Publication Pamphlet No. WO2013/059708A2
Harish M. Manohara et al., “Carbon Nanotube Schottky Diodes Using Ti-Schottky and Pt-Ohmic Contacts for High Frequency Applications,” Nano Letters, Vol. 5, No. 7, pp. 1469-1474, May 27, 2005
Unlike pn junction diodes in which majority carriers and minority carriers exist, only majority carriers exist in Schottky barrier diodes in which contact between metal and a semiconductor is utilized. Accordingly, Schottky barrier diodes operate at high speeds and are also suitable for use in, for example, a high-frequency region.
It is assumed that the above graphene nanoribbon or carbon nanotube is used for forming a Schottky barrier diode. Even if a Schottky barrier is formed on one electrode side, a decrease in contact resistance on the other electrode side may be insufficient. As a result, the formed Schottky barrier diode may fail to exhibit good diode characteristics.